INDUCTION AND PERSISTENCE OF PYRIMIDINE DIMERS IN EPIDERMAL DNA OF 2 STRAINS OF HAIRLESS MICE

Abstract

Carcinogenic UV light induction of DNA damage was measured in the epidermis of hairless mice with the use of damage specific endonucleases from Micrococcus luteus. The rates of induction of endonuclease sensitive sites in HRS/J/Anl and SKH:hairless-1 mice were 6.1 .+-. 0.5 .times. 10-11 and 6.5 .+-. 0.8 .times. 10-11/daltons per J per m2 from a FS40 fluorescent sun lamp (280-400 nm), respectively. Enzymatic photoreactivation with yeast photoreactivating enzyme showed that .apprx. 80% of the endonuclease sensitive sites were cyclobutyl pyrimidine dimers. In both strains of mice the pyrimidine dimers remained in high molecular weight DNA for 24 h after irradiation. These data show that mouse epithelial cells in vivo have little or no capacity for excision repair of pyrimidine dimers.